Imprinted polymer supports consist of an array of polymer imprints that are adhered to the surface of a substrate. One known method to prepare nano-sized imprinted polymer supports is Nano-Imprint Lithography (NIL). NIL involves providing an imprinting stamp having a plurality of imprint patterns formed thereon. A resin layer is also provided on a solid support substrate. The imprinting stamp is pressed into the resin layer while the resin is polymerised. The imprinting stamp is then removed and the imprint patterns are replicated in the polymer layer. To provide spatially distinct polymer imprints on the substrate, any polymer between the imprint patterns is removed by plasma etching to form spatially distinct polymer imprints on the substrate.
In conventional NIL, a polymer film needs to be spin-coated on the substrate before it can be imprinted by a hard mold. However, spin-coating is rather difficult on flexible substrates such as polymer membranes, which limits the capability of conventional NIL in patterning such substrates. Furthermore, as conventional NIL relies on viscous polymer flow to deform the polymer film and create the thickness contrast, elevated temperatures and pressures are required (L. J. Heyderman, H. Schift, C. David, J. Gobrecht and T. Schweizer, Microelectron. Eng., 54, 229 (2000); H. C. Scheer, H. Schulz, T. Hoffmann and C. M. S. Torres, J. Vac. Sci. Technol. B, 16, 3917 (1998); S. Zankovych, T. Hoffmann, J. Seekamp, J. U. Bruch and C. M. S. Torres, Nanotechnology, 12, (2001)). To achieve reliable pattern transfer, imprinting is typically performed at temperatures between 70 to 900 C above Tg (glass transition temperature) and under pressures as high as 10 MPa (L. J. Heyderman, H. Schift, C. David, J. Gobrecht and T. Schweizer, Microelectron. Eng., 54, 229 (2000); H. C. Scheer, H. Schulz, T. Hoffmann and C. M. S. Torres, J. Vac. Sci. Technol. B, 16, 3917 (1998); F. Gottschalch, T. Hoffmann, C. M. S. Torres, H. Schulz and H. Scheer, Solid-State Electron., 43, 1079 (1999)). Certain modifications to the conventional NIL technique such as the polymer bonding method developed by Borzenko et al (T. Borzenko, M. Tormen, G. Schmidt, L. W. Molenkamp, and H. Janssen, Appl. Phys. Lett., 79, 2246 (2001)) considerably reduce the temperature and pressure requirements. However, the polymer bonding method of Borzenko et al suffers the additional disadvantage of thick residue layer after imprinting, which complicates subsequent pattern transfer.
Imprinted polymer supports can be used in a number of applications. One such application is Solid Phase Organic Synthesis (SPOS). SPOS is an increasingly important technique in the field of organic synthesis, which offers several advantages over traditional synthesis in solution. SPOS is becoming a valuable alternative to traditional synthesis, particularly in applications that require a large number of different compounds in small quantities to be screened. SPOS is also used in combinatorial chemistry and in the production of compound libraries.
Solid phase synthesis uses insoluble support material as carriers for synthetic intermediates. Some of the important factors that affect the efficiency of the support materials are controlled swelling, available surface area, site isolation, chemical and mechanical stability and ease of separation. In addition to the type of polymer used, the geometry of the support material plays an important role to the above-mentioned parameters.
Various techniques have been adopted to identify polymeric supports that are more suitable for SPOS, including grafting to introduce functionality. Functionalised porous polymer beads have also been employed for SPOS, combinatorial chemistry, polymer supported catalysis and ion exchange resins.
One common drawback for the support materials prepared by the known techniques is the lack of design flexibility limited by geometrical constraints. In cross-linked polymer beads, most of the functionality of the beads is in the gel phase and hence the surface area of the beads is not critical. However, the swellability of the polymer is an important factor.
On inorganic supports there is no gel phase and all the active functionalities are immobilized on the surface of the support material. A large surface area will therefore be required to enhance the performance of SPOS by providing more active functionalities. The surface area of a solid particle is controlled by particle size. A larger surface can be achieved by reducing the particle size. However, due to handling problems during product separation, it is not advisable to go below a few microns in size. This is because after solid supported reaction of a product using beads, the beads immobilized with the product are normally separated by filtration. If the particle size of the bead is too small, it is difficult to filter. Centrifugation is also difficult as the polymer beads tend to float due to differences in the density differences.
There is a need to provide a method of producing an imprinted polymer support that overcomes, or at least ameliorates, one or more of the disadvantages described above.
There is a need to provide a method of fabricating nano/micro-sized polymer supports for SPOS which have reduced susceptibility to swelling.
There is a need to provide an array of nano/micro-sized polymer supports on a substrate which are spatially isolated.